The present invention generally pertains to subscriber communications systems and is particularly directed to an improved subscriber unit for wireless communication with a base station in a wireless digital subscriber communication system.
A typical subscriber unit is described in U.S. patent application Ser. No. 06/893,916 filed Aug. 7, 1986 by David N. Critchlow et al now issued as U.S. Pat. No. 4,825,448, dated Apr. 25, 1989. A base station used with such a subscriber unit in a wireless digital subscriber communication system is described in U.S. Pat. No. 4,777,633 to Thomas E. Fletcher, Wendeline R. Avis, Gregory T. Saffee and Karle J. Johnson. The subscriber unit described in application Ser. No. 06/893,916 includes means for transcoding a digital voice input signal to provide digital input symbols; means for FIR filtering the digital input symbols; means for deriving an analog intermediate frequency input signal from the filtered input symbols; means for combining the intermediate frequency input signal with an RF carrier for radio transmission to the base station; means for demodulating an output signal received from the base station to provide digital output symbols; and means for synthesizing a digital voice output signal from the digital output symbols. The subscriber unit includes a baseband processor chip and a modem processor chip. Both are TMS32020 digital signal processors. The baseband processor chip perform the transcoding of the digital voice input signal, the synthesis of the digital output symbols, and various baseband control functions; and the modem processor chip performs the FIR filtering of the digital input symbols, and the demodulation of the output signal received from the base station. The modem processor chip generally acts as the master for the system.